Group communication in differentiated services networks

The Differentiated Services (DiffServ) approach will also bring benefits for multicast applications which need quality of service support. For instance, a highly reliable multicast service can be provided based on the proposed expedited forwarding behavior. Such a service may also be used advantageously in a global computing cluster infrastructure, e.g., for distribution of synchronization messages. However, DiffServ multicast services have not been addressed in a very detailed manner yet. This paper illustrates some of the problems which will arise when IP Multicast is used in DiffServ networks without taking special precautions into account for providing it. Those problems mainly lead to situations in which other service users are affected adversely. In order to retain the benefits of the DiffServ approach, a quite simple and scalable solution for those problems is needed, not resulting in additional complexity or costs in a DiffServ domain. The proposed architecture in this paper requires only an additional entry for the DiffServ Codepoint in multicast routing tables and some support by management mechanisms. The discussion of the related problems and presentation of the solution is illustrated and confirmed by some measurements performed with a Linux implementation of DiffServ, and an adapted Linux multicast router.